Convert CONFIG_CONS_INDEX to Kconfig

This converts the following to Kconfig:
   CONFIG_CONS_INDEX

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/ls1028aqds_tfa_lpuart_defconfig b/configs/ls1028aqds_tfa_lpuart_defconfig
index e034827..f3475b5 100644
--- a/configs/ls1028aqds_tfa_lpuart_defconfig
+++ b/configs/ls1028aqds_tfa_lpuart_defconfig
@@ -75,6 +75,7 @@
 CONFIG_RTC_PCF2127=y
 CONFIG_SCSI=y
 CONFIG_DM_SCSI=y
+CONFIG_SPECIFY_CONSOLE_INDEX=y
 CONFIG_DM_SERIAL=y
 CONFIG_FSL_LPUART=y
 CONFIG_SPI=y